Generally, a polymer electrolyte fuel cell uses as fuel pure hydrogen or a hydrogen gas acquired by reforming alcohols, and generates electricity by electrochemically controlling a reaction of the hydrogen with oxygen in the air.
The polymer electrolyte fuel cell, which uses a solid, organic, hydrogen ion permselective membrane as an electrolyte, can be compactified as compared to conventional alkaline, phosphoric acid, molten carbonate, solid oxide or other fuel cells using an aqueous or fused salt electrolyte or other fluid medium as an electrolyte, and is under development for electric vehicles and other applications.
The polymer electrolyte fuel cell used, as shown in FIG. 1, has cells 5 each of which is of a sandwich structure provided by overlapping a separator 1 with formed convexes and concaves 1a and 1b, a hydrogen electrode 2, a polyelectrolyte membrane 3, an air (oxygen) electrode 4 and a separator 1 with formed convexes and concaves 1a and 1b. A number of cells 5 are stacked into a stack 6 to provide a hydrogen passage 7 defined by the separator 1 and the hydrogen electrode 2 in contact therewith, an air (oxygen) passage 8 defined by the separator 1 and the air electrode 4 in contact therewith and a cooling water passage 9 defined by the overlapped separators 1.
It is conventionally assumed that the separator 1 has a flat margin and a central bulge with a number of convexes and concaves 1a and 1b formed by press forming. However, actually attempted processing of a material made of sheet metal to be formed reveals that the press forming into the shape described above has difficulty since ductile fracture may occur in the bulge with the convexes and concaves 1a and 1b. Moreover, attempt of mass producing the separators 1 by press forming will problematically reduce the production efficiency.
In order to overcome the problems, it is recently proposed to oppositely arrange a pair of rolls having surfaces with forming areas with created convexes and concaves and to introduce and pressurize a material made of sheet metal to be formed between the rolls, thereby continuously producing a separator 1 with passages (hydrogen, air and cooling water passages 7, 8 and 9) formed correspondingly to the concaves and convexes of the rolls.
A state-of-the-art technology of an apparatus for producing a separator 1 for use in a polymer electrolyte fuel cell as shown in FIG. 1 is disclosed, for example, in Patent Literature 1.